First data collection

Second data collection

VLBW

ELBW

Z

VLBW

ELBW

Z

Sleep onset time, PM

22:06

(21:13 - 22:45)

21:09

(20:28 - 21:59)

2.61^**

21:41

(20:33 - 22:13)

21:33

(21:23 - 22:23)

−0.63

Sleep offset time, AM

6:21

(5:39 - 7:13)

7:05

(6:19 - 4:40)

2.02^*

6:57

(6:09 - 7:10)

6:11

(5:53 - 7:06)

−0.98

Nocturnal sleep duration (min)

394.0

(371 - 431)

436.5

(379 - 475)

−1.52

554.0

(512 - 580)

488.0

(448 - 565)

−0.08

Sleep efficiency (%)

81.2

(76.3 - 86.1)

74.4

(69.2 - 83.1)

2.10^*

97.2

(95.3 - 98.6)

97.0

(93.9 - 98.7)

−0.21

WASO (%)

99.0

(73.0 - 115.0)

146.5

(94.8 ? 171.3)

2.89^**

16.0

(8.0 - 27.0)

15.0

(6.0 - 32.5)

0.00

Number of night-waking

6.0

(4.5 - 8.0)

8.5

(7.0 - 10.3)

2.47^**

0.0

(0.0 - 1.0)

1.0

(0.0 - 2.5)

−0.62

Longest wake episode (min)

23.0

(19.5 - 27.5)

36.5

(21.0 - 42.3)

2.05^*

4.0

(3.0 - 7.0)

5.0

(2.0 - 10.0)

−0.31

Longest sleep episode (min)

100.0

(66.0 - 133.0)

92.5

(64.0 - 124.5)

−0.47

166.0

(108.0 - 222.0)

181.0

(125.5 - 198.5)

−0.10

Mean activity score

(count/min)

20.3

(15.7 - 24.9)

23.4

(17.7 - 30.4)

−1.47

9.7

(8.9 - 12.0)

10.3

(8.8 - 13.1)

−0.04

ACTX (%)

63.0

(56.5 - 69.0)

56.5

(46.5 - 58.3)

2.75^**

41.4

(34.7 - 43.4)

38.9

(33.1 - 42.6)

−0.56